Deflection plates coated with secondary electron emissionsuppressing metal



Feb. 6, 1968 OSAMU YOSHIDA ETAL 3,368,095

v DEFLECTION PLATES COATED WITH SECONDARY ELECTRON EMISSION-SUPPRESSING METAL Original Filed Aug. 26, 1964 ma 9 2771244, mwu

ATTORNEYS United States Patent 3,368,096 DEFLECTION PLATES COATED WITH SECONDARY ELECTRON EMISSION- SUPPRESSING METAL Osamu Yoshida, Kyoto, Shigeya Ashizaki, I-Iirakata-shi, and Masaharu Kaname, Kyoto, Japan, assignors to Matsushita Electronics Corporation, Osaka, Japan, a corporation of Japan Continuation of application Ser. No. 392,170, Aug. 26, 1964. This application Apr. 19, 1967, Ser. No. 632,109 Claims priority, application Japan, Aug. 31, 1963, 38/ 66,149 2 Claims. (Cl. 313--80) This application is a continuation of application Serial No. 392,170, now abandoned.

This invention relates to improvements relating to methods of manufacturing cathode-ray tubes with electrostatic deflection and cathode-ray tubes manufactured by such methods.

In cathode-ray tubes with electrostatic deflection it is in many cases diflicult to obtain a sharply-defined luminous spot on the fluorescent screen. Also it is found that these difl'lculties are experienced to a different extent with tubes of the same type. Furthermore the differences from the desired dimensions of the luminous spot have been found to be greater if the deflection sensitivity of the cathode-ray is increased either by arranging the deflection plates in closer proximity to each other, or decreasing the velocity of electrons.

The inventor has found that the difliculties referred to are substantially attributable to impurities present on the inner surfaces of the deflection plates, that is on those surfaces of the deflection plates which are adjacent to each other. It is supposed that the impurities, which may consist of metal oxides and other impurities which may get on the surfaces of the deflection plates during assembling the electrode system, may cause undesirable stray of the electrons, for example, due to reflection of primary electrons and secondary emission.

The above-mentioned difliculties are avoided by the method in accordance with the invention which is characterized by arranging at least one thin metal plate laterally in front of each set of the deflection plates, the metal of the metal plate, after exhaustion of the tube, being evaporation-deposited on the inner surfaces of the deflection plates for forming thereon a glossy conductive layer. Since the impurities are now covered by a pure, glossy conductive layer, they can no longer exert any influence on the electrons. Due to the fact that the reflections of primary electrons off the surface layers of the deflection plates, which are of pure metal, are invariably the same and substantially no secondary emission occurs, allowance may be made for any differences in constructing the deflection plates, resulting in a sharplydefined electron spot of small cross-section being obtained. In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIGURE 1 shows part of a cathode-ray tube; and

FIGURE 2 shows the set of deflection plates.

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In FIGURE 1 the electron gun is indicated by 1. Thin nickel plates 2 and 4 are arranged respectively laterally in front of deflection plates 3 for vertical deflection and laterally in front of deflection plates 5 for horizontal deflection. As for the deflection plates 3 and 5, plates with finely rugged surface may be preferably used to avoid the detrimental effect caused by ballistic reflection of electron beam. The glass envelope of the tube is noted by reference numeral 6. Nickel and niEkel-chrome alloys have been found to be suitable metals for the plates 2 and 4 since they hardly emit any secondary electrons.

After exhaustion of the tube, the plates 2 and 4 are heated, preferably by high frequency induction currents, so that the metal of the plates is evaporated and deposited as a glossy pure metal on the inner surfaces of the deflection plates 3 and 5, respectively, the layer wholly covering any impurities present on the surfaces. It will be evident that the precipitation of metal vapor at undesired areas may be prevented by providing shields and by correct positioning and shaping of the plates 2 and 4 respectively.

What is claimed is:

1. A cathode-ray tube with electrostatic deflection and including an evacuated envelope at one end of which is an electron gun for emitting an electron beam and at the other end of which is a fluorescent screen to be bombarded by said electron beam, said cathode ray tube comprising at least one pair of horizontal deflection plates arranged in opposing relationship on opposite sides of the path of said electron beam, a first thin, pure metal plate initially mounted in a plane intersecting with the inner surfaces of said horizontal deflection plates at a right angle to and exterior of the path of said electron beam, said metal plate subsequently forming a thin evaporation-deposited secondary electron emission suppressing metal layer on the inner surfaces of each said horizontal deflection plate when heated, at least one pair of vertical deflection plates arranged in opposing relationship on opposite sides of the path of said electron beam and in a plane intersecting with said horizontal deflection plates at a right angle, and a second thin, pure metal plate initially mounted in a plane intersecting with the inner surfaces of said vertical deflection plates at a right angle to and exterior of the path of said electron beam, said second metal plate subsequently forming a thin evaporationdeposited secondary electron emission suppressing metal layer on the inner surfaces of each said vertical deflection plate when heated.

2. A cathode-ray tube according to claim 1, wherein said first and second thin, pure metal plates comprise a metal selected from the group consisting of nickel and nickel-chrome alloy.

References Cited UNITED STATES PATENTS 2,244,260 6/1941 Power 313- X 2,336,895 12/1943 Shelton et al. 313-107 X ROBERT SEGAL, Primary Examiner. 

1. A CATHODE-RAY TUBE WITH ELECTROSTATIC DEFLECTION AND INCLUDING AN EVACUATED ENVELOPE AT ONE END OF WHICH IS AN ELECTRON GUN FOR EMITTING AN ELECTRON BEAM AND AT THE OTHER END OF WHICH IS A FLUORESCENT SCREEN TO BE BOMBARDED BY SAID ELECTRON BEAM, SAID CATHODE RAY TUBE COMPRISING AT LEAST ONE PAIR OF HORIZONTAL DEFLECTION PLATES ARRANGED IN OPPOSING RELATIONSHIP ON OPPOSITE SIDES OF THE PATH OF SAID ELECTRON BEAM, A FIRST THIN, PURE METAL PLATE INITALLY MOUNTED IN A PLANE INTERSECTING WITH THE INNER SURFACES OF SAID HORIZONTAL DEFLECTION PLATES AT A RIGHT ANGLE TO AND EXTERIOR OF THE PATH OF SAID ELECTRON BEAM, SAID METAL PLATE SUBSEQUENTLY FORMING A THIN EVAPORATION-DEPOSITED SECONDARY ELECTRON EMISSION SUPPRESSING METAL LAYER ON THE INNER SURFACES OF EACH SAID HORIZONTAL DEFLECTION PLATE WHEN HEATED, AT LEAST ONE PAIR OF VERTICAL DEFLECTION PLATES ARRANGED IN OPPOSING RELATIONSHIP ON OPPOSITE SIDES OF THE PATH OF SAID ELECTRON BEAM AND IN A PLANE INTERSECTING WITH SAID HORIZONTAL DEFLECTION PLATES AT A RIGHT ANGLE, AND A SECOND THIN, PURE METAL PLATE INITIALLY MOUNTED IN A PLANE INTERSECTING WITH THE INNER SURFACES OF SAID VERTICAL DEFLECTION PLATES AT A RIGHT ANGLE TO AND EXTERIOR OF THE PATH OF SAID ELECTRON BEAM, SAID SECOND METAL PLATE SUBSEQUENTLY FORMING A THIN EVAPORATIONDEPOSITED SECONDARY ELECTRON EMISSION SUPPRESSING METAL LAYER ON THE INNER SURFACES OF EACH SAID VERTICAL DEFLECTION PLATE WHEN HEATED. 